route from Yakima to SeaTac?

Can anyone suggest a route for a 2 day ride? Google maps says either the I-90 corridor using side roads & Iron Horse Trail, or a combination of Hwy 410 and forest roads. I live in Arizona, so I don't know the riding conditions on either route. I have heard the Iron Horse is gravel, so that sounds like a road bike with 23mm tires is out. Google Earth seems to show some form of pavement on the entire southern route, but no towns.

My main concerns are:
safety re: car traffic - so either closed trails or safe roads
food & lodging near the pass
what tires / type of bike to use - I can build up anything required


Hwy 410 will work OK for you, if you're riding during the summer when it's open. Automobile traffic is pretty sedate on a weekday - it's busier with recreational traffic on a weekend. Last month I rode up from Enumclaw up to Sunrise on a weekday and found wide shoulders, limited motor vehicle traffic, big shady trees, and pretty views. Food and lodging is possible on 410, but you'll need to hunt around and be sure to have something reserved in advance. A weekday would be a lot easier than a weekend to find a place to stay. Alta Crystal is just off of 410, but I'm not sure if it has restaurant. There's more services up at the actual Crystal Mountain Ski Area, but you may not be keen on having to climb a steep 6 miles to reach it. 



A road bike is just fine on 410 - and dang, it would be so much more scenic than I-90. I know which one I'd choose!